The present invention relates to methods and apparatus for reducing the amount of residual injection fluid within an injection pump after an associated internal combustion engine is shut off. More particularly, the present invention relates to methods and apparatus for reducing amount of the residual injection fluid within a distributor injection pump including an injection timing mechanism, after a stop valve, such as an electro-magnetic stopping device, on the pump is closed.
The present invention is mainly concerned with distributor injection pumps. A distributor injection pump has only one pumping element for all of the cylinders of an internal combustion engine. A piston in the distributor injection pump delivers the fuel via a lifting movement and distributes it to individual outlets via a rotary motion. During one revolution of the piston around a driving shaft, the piston executes as many strokes as there are engine cylinders to supply.
One disadvantage associated with distributor injection pumps is that even though an electrical stop valve (such as an "ELAB") shuts off the internal combustion engine, a significant amount of residual fuel is still injected. This condition can lead to engine damage and accidents. This condition is typically caused by the collection of fuel within the reset area of the pump during the "bottom dead-point movement" (UT-movement) of the pump's piston upon the closure of the stop valve. The quantity of fuel collected depends on the time cross-section of the reset area, which varies with rotational speed, with the instant that the delivery of fuel ends, with the configuration of the reset area, and with the prevailing pressure in the interior space of the pump.
German Published Patent Application No. 33 04 335 discloses a control system for stopping the operation of an internal combustion engine. In normal operation, fuel is sucked in from a fuel tank and directed to the suction chamber of an injection pump via a delivery pipe. A separate suction device is provided to shut off the internal combustion engine. The separate suction device is connected on its suction side to the suction chamber of the injection pump. The suction device aspirates the fuel from the suction chamber when the operation of the internal combustion engine is stopped.